Stylus pen

ABSTRACT

An exemplary embodiment of the present invention provides a stylus pen including: a body; a conductive tip configured to be exposed from an inside of the body to an outside thereof; and a resonance circuit connected to the conductive tip to resonate an electrical signal transferred from the conductive tip. An inductor unit of the resonance circuit includes a ferrite core and a coil wound in multiple layers over at least a portion of the ferrite core. The ferrite core includes nickel, and the coil can be formed by a litz wire with adjacent winding layers that are wound to be inclined in a zigzag form.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a Continuation Application of U.S. patentapplication Ser. No. 16/790,853 filed on Feb. 14, 2020, which claimspriority to and benefits of Korean Patent Application No.10-2019-0017373, filed in the Korean Intellectual Property Office onFeb. 14, 2019, the entire contents of which are incorporated herein byreference.

BACKGROUND OF THE INVENTION (a) Field of the Invention

The present disclosure relates to a stylus pen.

(b) Description of the Related Art

Various terminals such as mobile phones, smart phones, tablet PCs,laptop computers, digital broadcasting terminals, PDAs (personal digitalassistants), PMPs (portable multimedia players), and navigation devicesinclude touch sensors.

In such a terminal, a touch sensor may be disposed on a display paneldisplaying an image, or may be disposed in an area of a terminal body.As a user interacts with the terminal by touching the touch sensor, theterminal may provide the user with an intuitive user interface.

The user may use a stylus pen for sophisticated touch input. The styluspen may be classified into an active stylus pen and a passive stylus pendepending on whether a battery and an electronic component are providedtherein.

The active stylus pen may have better basic performance as compared withthe passive stylus pen and provide additional functions (pen pressure,hovering, and buttons), but the pen itself is expensive and requires apower source to charge the battery, so there are not many users exceptfor some advanced users.

The passive stylus pen is inexpensive and requires no battery comparedto the active stylus pen, but has difficult touch recognition ascompared to the active stylus pen. However, recently, techniques of aninductive resonance type of an EMR (Electro Magnetic Resonance) methodand a capacitive resonance method have been proposed in order toimplement a passive stylus pen capable of sophisticated touchrecognition.

The EMR method is superior in writing/drawing quality, which is a keyfeature of the stylus pen, but is thicker and more expensive since aseparate EMR sensor panel and an EMR driving IC must be added inaddition to the capacitance touch panel.

The capacitive resonance method uses a general capacitance touch sensorand a touch controller IC to support the pen touch by increasing theperformance of the IC without additional cost.

In the capacitive resonance method, the amplitude of a resonance signalmust be large for the touch sensor to more accurately identify the touchby the stylus pen, and thus a frequency of the driving signaltransferred from the touch sensor to the stylus pen is almost equal to aresonance frequency of a resonance circuit built in the stylus pen.However, depending on the conventional capacitive resonance method, evenwhen the resonance frequency and the frequency of the drive signalcoincide with each other, attenuation of signal transmission becomesvery large due to very small capacitance formed between a touch sensorthat outputs the drive signal and a pen tip that receives the drivesignal, thereby making signal transmission difficult. As a result,despite a long attempt by many touch controller IC vendors, there are nocompanies that have succeeded in mass production because sufficientoutput signals are not obtained.

Therefore, how to design the internal resonance circuit and penstructure is a very important factor in manufacturing capacitiveresonant stylus pens that can produce maximum output signals.

The above information disclosed in this Background section is only forenhancement of understanding of the background of the invention andtherefore it may contain information that does not form the prior artthat is already known in this country to a person of ordinary skill inthe art.

SUMMARY OF THE INVENTION

The present exemplary embodiments have been made in an effort to providea capacitive resonant stylus pen capable of generating sufficient outputsignals.

For achieving the objects or other objects, an exemplary embodiment ofthe present invention provides a stylus pen including:

a body; a conductive tip configured to be exposed from an inside of thebody to an outside thereof; an inductor unit including a ferrite coredisposed in the body and a coil connected to the conductive tip andwound in multiple layers over at least a portion of the ferrite core;and a capacitor unit disposed in the body to be electrically connectedto the inductor unit to form a resonance circuit.

Herein, the ferrite core may have permittivity of 1000 F/m or less, andthe coil has a form where adjacent winding layers are alternately wound,and the coil is a wire covering two or more insulated wires.

In addition, the ferrite core may include nickel, and the coil may beformed of a litz wire.

It may further include a ground portion that can be electricallyconnected to the user, it may further include a bobbin surrounding atleast a portion of the ferrite core, and the coil may be wound over atleast a portion of the bobbin.

It may further include a conductive blocking member configured tosurround at least a portion of the resonance circuit. The blockingmember may include one slit for blocking generation of eddy currents,and opposite ends of the blocking member may be spaced apart by the slitin a first direction in which an eddy current is formed.

Another exemplary embodiment of the present invention provides a styluspen including: a body; a conductive tip configured to be exposed from aninside of the body to an outside thereof; a resonance circuit disposedin the body to be connected to the conductive tip and to resonate anelectrical signal transferred from the conductive tip; and a groundportion configured to be capable of being electrically connected to auser.

Herein, the resonance circuit may include: an inductor unit configuredto include a ferrite core disposed in the body and a coil electricallyconnected to the conductive tip and wound in multiple layers over atleast a portion of the ferrite core; and a capacitor unit disposedwithin the body to be electrically connected to the ground portion andthe conductive tip. In this case, the ferrite core may have permittivityof 1000 F/m or less, the coil is zigzag wound so that adjacent windinglayers are inclined, and the coil may be a wire covering two or moreinsulated wires.

In addition, the ferrite core may include nickel, and the coil may beformed of litz wire.

In this case, the resonance circuit may be formed to include two or moreinductor units and one capacitor unit connected in series. In addition,the resonance circuit may include two or more LC resonance circuits thatare connected in series.

It may further include a conductive blocking member configured tosurround at least a portion of the resonance circuit. The blockingmember may include one slit for blocking generation of eddy currents,and opposite ends of the blocking member may be spaced apart by the slitin a first direction in which an eddy current is formed.

The effects of the stylus pen according to the present disclosure willbe described as follows.

According to at least one of the exemplary embodiments of the presentdisclosure, a sufficient output signal may be generated even with a thindiameter by presenting the structure of the resonance circuit of theoptimal capacitive resonant stylus pen.

According to at least one of the exemplary embodiments of the presentdisclosure, it is possible to provide a stylus pen that is robustagainst external factors.

The additional range of applicability of the present disclosure willbecome apparent from the following detailed description. However, sincevarious modifications and alternatives within the spirit and scope ofthe present disclosure may be clearly understood by those skilled in theart, it is to be understood that a detailed description and a specificexemplary embodiment of the present invention are provided only by wayof example.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a schematic view showing a stylus pen and a touchsensor.

FIG. 2 illustrates a stylus pen and a touch sensor in detail.

FIG. 3 illustrates an inductor unit of the stylus pen in detail.

FIG. 4 illustrates inductance and Q values depending on frequencychanges.

FIG. 5 and FIG. 6 respectively illustrate an enamel wire and a litzwire.

FIG. 7A and FIG. 7B illustrate a multi-layer winding method.

FIG. 8 to FIG. 10 illustrate graphs showing results of comparativeexperiments.

FIG. 11 illustrates another example of the inductor unit.

FIG. 12 and FIG. 13 are graphs illustrating the magnitude of a resonancesignal depending on the structure of the inductor unit.

FIG. 14 and FIG. 15 illustrate other examples of the resonance circuit.

FIG. 16 illustrates an equivalent circuit showing an effect of parasiticcapacitance of a user's hand.

FIG. 17 illustrates a schematic view showing a stylus pen of an LLCstructure.

FIG. 18A to FIG. 18D illustrate various examples of a blocking member.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The present invention will be described more fully hereinafter withreference to the accompanying drawings, in which exemplary embodimentsof the invention are shown. As those skilled in the art would realize,the described embodiments may be modified in various different ways, allwithout departing from the spirit or scope of the present invention.

To clearly describe the present invention, parts that are irrelevant tothe description are omitted, and like numerals refer to like or similarconstituent elements throughout the specification.

In addition, unless explicitly described to the contrary, the word“comprise” and variations such as “comprises” or “comprising” will beunderstood to imply the inclusion of stated elements but not theexclusion of any other elements. When referring to a part as being “on”or “above” another part, it may be positioned directly on or above theother part, or another part may be interposed therebetween. In contrast,when referring to a part being “directly above” another part, no otherpart is interposed therebetween.

FIG. 1 illustrates a schematic view showing a capacitive resonant styluspen and a touch sensor. As illustrated in FIG. 1, a stylus pen 10 and atouch sensor 20 may be close to each other.

The stylus pen 10 may include a conductive tip 11, a resonance circuit12, a ground portion 18, and a body 19.

The conductive tip 11 is connected with the resonance circuit 12. All orpart of the conductive tip 11 may be formed of a conductive material(e.g., a metal, graphite, a conductive rubber, a conductive fabric, aconductive silicon, etc.). In addition, the conductive tip 11 may have aform in which a portion of the conductive tip 11 is exposed to anoutside of a non-conductive housing while being present inside thenon-conductive housing, but it is not limited thereto.

The resonance circuit 12 may resonate with a driving signal that isinputted from the touch sensor 20. For example, the resonance circuit 12may be an LC resonance circuit, and may resonate with a driving signalthat is received from the touch sensor 20 through the conductive tip 11.The driving signal may be a Tx signal that is transferred to the touchelectrode (channel). For example, the driving signal may include asignal (e.g., a sine wave, a square wave, etc.) having a frequencycorresponding to the resonance frequency of the stylus pen 10 so as toallow the stylus pen 10 to generate a resonance signal by capacitivecoupling or electromagnetic resonance.

The resonance circuit 12 may output a resonance signal caused byresonance to the conductive tip 11 during a period in which a drivingsignal is inputted and during a partial period thereafter. The resonancecircuit 12 is disposed in the body 19 to be connected to the groundportion 18. The ground portion 18 may be grounded by a body of a userwho contacts an outer surface of the body 19.

The body 19 may accommodate elements of the stylus pen 10. In FIG. 1,the body 19 is illustrated in a form in which a horn portion and apillar portion are integrally combined, but the two portions may beseparated. It may have a cylindrical shape, a polygonal shape, a columnshape having at least part of a shape of a curved surface, an entasis, afrustum of a pyramid, a circular truncated cone, or the like, but it isnot limited thereto. Since the body 19 is empty inside, the body 19 mayaccommodate the conductive tip 11, the resonance circuit 12, and theground portion 18 therein.

The touch sensor 20 may include a channel electrode 21 and a window 22disposed at an upper portion of the channel electrode 21. The channelelectrode 21, the conductive tip 11, and the window 22 may constitutecapacitor Cx.

FIG. 2 illustrates a schematic view showing a stylus pen and a touchsensor in detail.

First, as illustrated in FIG. 2, the stylus pen 10 includes a conductivetip 11, a capacitor unit 13, an inductor unit 14, a ground portion 18,and a body 19. The capacitor unit 13 and the inductor unit 14 constitutethe resonance circuit 12 of FIG. 1.

The conductive tip 11 may be connected to the capacitor unit 13 and/orthe inductor unit 14 through a conductive connection member, and theconductive connecting member may be a wire, a pin, a rod, a bar, or thelike, but it is not limited thereto. In addition, the conductiveconnection member may include a coil of the inductor unit 14.

The capacitor unit 13 may include a plurality of capacitors connected inparallel. The capacitors may have different capacitances, and may betrimmed in a manufacturing process.

The inductor unit 14 may be disposed adjacent to the conductive tip 11.The inductor unit 14 includes a ferrite core and a coil that is woundaround the ferrite core.

The capacitor unit 13 and the inductor unit 14 are connected inparallel, and a resonance signal is generated in response to a drivingsignal through LC resonance of the capacitor unit 13 and the inductorunit 14. FIG. 3 illustrates a schematic view showing an inductor unit ofa stylus pen in detail.

Referring to FIG. 3, the inductor unit 14 includes a ferrite core 15 anda coil 16 that is wound around the ferrite core 15.

In this case, the inductance of the inductor unit 14 is determined bythe following Equation 1.

$\begin{matrix}{L = \frac{\mu SN^{2}}{l}} & \left( {{Equation}\mspace{14mu} 1} \right)\end{matrix}$

As can be seen from Equation 1, the inductance is proportional to thepermeability of the ferrite core 15, a cross-sectional area of the coil16, and a square of a number of turns, and is inversely proportional toa winding length of the coil 16.

A design of the inductor unit 14 is very important in the resonancecircuit 12 accommodated in the capacitive resonant stylus pen. Inparticular, in the design of the inductor unit, inductance L and a Qvalue are very important parameters as illustrated in FIG. 4. Herein,the Q value is an amount representing a coil characteristic as aresonance circuit element, and is given by an equation Q=2πfL/R. Inaddition, L and R indicate the inductance and resistance of the coil,respectively, and f indicates the frequency. The higher the Q value, thesharper the resonance characteristic.

In the design of the capacitive resonant stylus pen, L may have asufficiently large self-resonance frequency relative to a frequency tobe used, and the Q value may have a maximum at a frequency to be used.To satisfy this, it is necessary to optimize a material of the ferritecore, a wire type of the coil, and a winding scheme. There is also aneed for a method that can obtain a high output signal while maintainingthe diameter of a thin pen.

In the following exemplary embodiments, a design method of a capacitiveresonant stylus pen that is most optimized among materials of aplurality of ferrite cores, wire types of coils, and a winding schemewill be described.

1. Ferrite Core Material

In an example, manganese (Mn) and nickel (Ni) were used as a ferritecore material.

2. Wire Type

In the example, an enameled wire and a litz wire were used as the wiretype of the coil used.

As illustrated in FIG. 5, an enameled wire 100 is an electric wire madeby coating an insulating enamel 102 on a surface of a copper wire 101and heating it to a high temperature, and is used for winding and wiringof electrical devices, communication devices, and electricalinstruments. In the example, an enameled wire having a total thickness Tof 0.2 mm, an electric wire diameter Φ of 0.18 mm, and a coatingthickness t of 0.01 mm was used.

As illustrated in FIG. 6, a litz wire 200 is a special insulated wirethat is made by twisting several strands of a thin insulated wire 100(e.g., an enameled wire) having a diameter of about 0.1 mm as one wireand applying an insulating coating 201 made of nylon or the likethereon. The litz wire 200 may reduce a skin effect by increasing asurface area, and is used for coils of high frequency circuits and thelike.

In the example, a litz wire having a total thickness T of 0.2 mm, anelectric wire diameter Φ of 0.06 mm, and a covering thickness t of 0.007mm was used.

3. Winding Scheme

In the example of the present invention, a winding scheme of amultilayer winding structure is used in order to obtain a sufficientinductance value (that is, a sufficient number of turns) in a limitedspace of a stylus pen. Specifically, as shown in FIG. 7A and FIG. 7B,two kinds of multi-layer winding schemes were used.

The winding scheme of FIG. 7A is a simplest winding scheme, and is asequential layer winding scheme in which an upper layer is wound afterwinding of a lower layer that is disposed immediately therebelow isfinished. In this case, the scheme of FIG. 7A is a scheme in whichwinding of a layer starts at a point where winding of a previous layerthat is disposed immediately therebelow ends, and is hereinafterreferred to as a U-type winding scheme.

The winding scheme of FIG. 7B is an alternate layer winding scheme inwhich adjacent winding layers are alternately wound, such that windingsof adjacent layers are wound in a zigzag form. Hereinafter, this isreferred to as a zigzag winding scheme. This zigzag winding scheme mayminimize a voltage difference between the windings of adjacent layers,thereby reducing winding self-capacitance. In this case, the windingself-capacitance, which is a kind of parasitic capacitance, is aparameter representing electric field energy stored in the winding.

Comparative Experiment 1 (Comparison of Characteristic Values for EachMaterial

A material of the ferrite core was changed to manganese, nickel, andmagnesium, and the Q value was measured in a state where an enameledwire was used as a wire type of coil and was wound by a U type ofwinding scheme.

As a result of the measurement, there was little difference between thecharacteristics of the Q values for each material of cores, and ameasured Q value was not enough to be implemented as a product.

Comparative Experiment 2 (Comparison of Characteristic Values for EachType of Windings)

Q values were respectively measured for the Inductors 1 and 2 producedusing the enameled wire and the litz wire in a state in which theferrite core was wound with manganese (Mn) by the U type of windingscheme.

FIG. 8 illustrates Q values of Inductors 1 and 2 measured while changingfrequencies through an E4980A precision LCR meter manufactured byKEYSIGHT TECHNOLOGIES.

In FIG. 8, a indicates a waveform showing a change in the Q value withrespect to the frequency of Inductor 1 (manganese core/enameledwire/U-type winding scheme), and b indicates a waveform showing a changeof the Q value with respect to the frequency of the Inductor 2(manganese core/litz wire/U-type winding scheme).

The Q value has almost a maximum at a frequency (frequency f1) around400 kHz in the Inductor 2 manufactured by the Litz wire, and the Q valuehas almost a maximum at a frequency (frequency f2) around 150 kHz in theInductor 1 manufactured by the enameled wire.

As a result of comparing a and b of FIG. 8, it can be seen that themaximum Q value of the Inductor 2 is about 1.5 times higher than themaximum Q value of the Inductor 1. Accordingly, it can be seen that thelitz wire is superior to the enameled wire as the coil of the inductorforming the resonance circuit of the stylus pen.

However, the maximum Q value of Inductor 2 measured in ComparativeExperiment 2 was about ½ of a target value Q_(target) required forcommercialization.

Comparative Experiment 3 (Comparison of Characteristic Values for EachWinding Scheme)

Q values were measured for the inductors 3 to 5 manufactured by changingthe wire type to the enameled wire and the litz wire and the windingscheme to the U type and the zigzag type in a state where the ferritecore was made of manganese (Mn).

FIG. 9 illustrates Q values of Inductors 3 to 5 measured while changingfrequencies through an E4980A precision LCR meter manufactured byKEYSIGHT TECHNOLOGIES.

In FIG. 9, a indicates a waveform showing a change in the Q value withrespect to the frequency of Inductor 3 (manganese core/enameledwire/U-type winding scheme), b indicates a waveform showing a change ofthe Q value with respect to the frequency of Inductor 4 (manganesecore/enameled wire/zigzag winding scheme), and c indicates a waveformshowing a change of the Q value with respect to the frequency ofInductor 5 (manganese core/litz wire/zigzag winding scheme)

As can be seen from the waveform c of FIG. 9, the Q value has almost amaximum at a frequency (frequency f3) around 300 kHz in Inductor 5manufactured by the litz wire/zigzag winding scheme. The Q value hasalmost a maximum at a frequency (frequency f2) around 150 kHz inInductor 4 manufactured by the enameled wire/zigzag winding scheme andInductor 3 manufactured by the enameled wire/U-type winding scheme.

In addition, as a result of comparing a, b, and c of FIG. 9, it can beseen that the maximum Q value of Inductor 5 is about 1.5 times higherthan the maximum Q value of the Inductor 4 and is twice or more higherthan the maximum Q value of Inductor 3. Accordingly, it can be seen thatthe zigzag type is superior to the U-type as the winding scheme of theinductor forming the resonance circuit of the stylus pen.

However, the maximum Q value of Inductor 5 (manganese core/litzwire/zigzag winding scheme) measured in Comparative Experiment 2 wasabout ¾ of a target value Q_(target) required for commercialization.

Comparative Experiment 4 (Comparison of Characteristic Values for EachCore Material)

In this example, manganese and nickel were used as a ferrite corematerial, and it is known that permeability of nickel is generally200-300, and the permeability of manganese is generally 3000-5000.

Since the manganese used in this example is approximately 15 timeshigher in permeability than nickel, assuming that the coils have samecross-sectional area and length, the number of turns of manganese isreduced by approximately four times that of nickel to obtain the sameinductance value. Accordingly, only from the viewpoint of the number ofturns, it can be seen that is more effective to use manganese thannickel.

On the other hand, since the inductor unit 14 has a complicatedstructure including a coil wound around the core, parasitic capacitanceis additionally generated. Since the Q value decreases due to suchparasitic capacitance, an amplitude of the resonance signal may bereduced.

The parasitic capacitance generated in the inductor unit 14 may occurbetween the wound coils and between the core and the coil, and asdescribed above, the parasitic capacitance between the wound coils maybe reduced by adopting the zigzag winding scheme.

Meanwhile, in this example, a core material having lower permittivitythan that of manganese was tested in order to reduce the parasiticcapacitance between the core and the coil, and the test result confirmedthat the nickel core was an optimal material for the ferrite core.

An important physical property in manganese and nickel, which are mainlyused as a ferrite core element, is permeability, which has an importanteffect on an inductance value as shown in Equation 1. However, inmanganese and nickel as ferrite elements, the permittivity is a physicalproperty of little concern, and in fact, nickel does not have relevantinformation in the data sheet provided by the manufacturer.

In this example, the permittivity of manganese and nickel was measuredusing E4980A precision LCR meter of KEYSIGHT TECHNOLOGIES in order toconfirm the permittivity of manganese and nickel, and the measurementresults are shown in Table 1 below.

TABLE 1 Manganese permittivity Nickel permittivity Measurement 1 2400 —Measurement 2 8300 2

Measurements 1 and 2 were measured using the same E4980A precision LCRmeter of KEYSIGHT TECHNOLOGIES, where Measurement 1 represents thepermittivity that is automatically calculated by measurement software.According to Measurement 1, although the permittivity of manganese is2400, the permittivity of nickel is not measured.

Measurement 2 is a method of calculating the dielectric constant bymeasuring capacitance, area, and distance between ferrite cores, andaccording to Measurement 2, the permittivity of manganese is 8300 andthe permittivity of nickel is 2.

There is a big difference in the result of permittivity betweenMeasurement 1 and Measurement 2, and in the case of Measurement 2, itwas confirmed that errors were considerable depending on capacitance,area, distance, and the like. However, as results of Measurement 1 andMeasurement 2, it can be seen that nickel has permittivity of at least1/1000 or more relative to manganese.

In Comparative Experiment 4, Q values were measured for Inductors 6 and7 manufactured by changing the winding type to the U type and the zigzagtype with the ferrite core made of nickel and using the litz wire as thewire type.

FIG. 10 illustrates Q values of Inductors 6 and 7 measured whilechanging frequencies through an E4980A precision LCR meter manufacturedby KEYSIGHT TECHNOLOGIES.

In FIG. 9, a indicates a waveform showing a change in the Q value withrespect to the frequency of Inductor 6 (nickel core/litz wire/U-typewinding scheme), and b indicates a waveform showing a change of the Qvalue with respect to the frequency of the Inductor 7 (nickel core/litzwire/zigzag winding scheme).

As can be seen from the waveform b of FIG. 10, the Q value has almost amaximum at a frequency (frequency f5) around 400 kHz in Inductor 7manufactured by the nickel core/litz wire/zigzag winding scheme. The Qvalue has almost a maximum at a frequency (frequency f6) around 200 kHzin Inductor 6 manufactured by the nickel core/litz wire/U-type windingscheme. As a result of comparing a and b of FIG. 11, it can be seen thatthe maximum Q value of Inductor 7 is about two times higher than themaximum Q value of Inductor 6.

The maximum Q value of Inductor 7 (nickel core/litz wire/zigzag windingscheme) measured in Comparative Experiment 4 almost reaches a targetvalue Q_(target) required for commercialization.

In Comparative Experiments 1 to 4 described above, inductors weremanufactured and tested for Q values by changing the material of theferrite core, the wire type of the coil, and the winding scheme, andtest results show that the highest Q value is obtained when the inductorunit of the capacitive resonant stylus is designed by winding of thenickel core, the litz wire, and the zigzag winding scheme. In addition,it can be seen that the maximum Q value of the inductor manufactured bythis combination reaches the target value Q_(target) forcommercialization.

Meanwhile, in the present exemplary embodiment, the nickel core is usedas the ferrite core and the litz wire is used as the wire type of thecore, but similar results may be obtained when a material withpermittivity of 1000 or less is used as the ferrite core instead of thenickel core, and a single wire wrapped with two or more insulatedstrands is used instead of the litz wire.

In the present exemplary embodiment, as described below, a method ofincreasing the distance between the core and the coil by providing abobbin between the core and the coil may be used in order to furtherreduce the parasitic capacitance between the core and the coil, inaddition to using nickel having lower permittivity than manganese.

Referring to FIG. 11, the inductor unit 14 includes a ferrite core 15, abobbin 141 surrounding at least a portion of the ferrite core 15, and acoil 16 wound on at least a portion of the bobbin 141. The bobbin 141may be fixed by being closely adhered to the ferrite core 15 by a forcecaused by the winding of the coil 16. The bobbin 141 may include thesame material as that of the body 19 or a different material, and mayinclude, e.g., a plastic or metal having an insulating surface.Specifically, polyphenylene sulfide (PPS), liquid crystalline polyester(LCP), polybutylene terephthalate (PBT), polyethylene terephthalate(PET), a phenolic resin, or the like may be used for the bobbin 141.

As such, when the bobbin 141 covers the ferrite core 15 and the bobbin141 is wound as the coil 16, a distance between the ferrite core 15 andthe coil 16 increases, so that a value of a parasitic capacitance Cp2 inFIG. 11 may be set to be smaller than a value of a parasitic capacitanceCp1 in FIG. 3.

Referring to FIG. 12, when the inductor unit 14 includes only theferrite core 15 and the coil 16, a maximum amplitude of the resonancesignal is measured to be about 2 V (+1 V to −1 V). Referring to FIG. 13,when the inductor unit 14 includes the ferrite core 15, the bobbin 141,and the coil 16, the maximum amplitude of the resonance signal ismeasured to be about 4 V (+2 V to −2 V). That is, when at least aportion of the ferrite core 15 is surrounded in the bobbin 141 and thecoil 16 is wound on the bobbin 141, it is confirmed that the amplitudeof the resonance signal is larger.

Meanwhile, in the case of using nickel as the ferrite core to design theoptimum inductor unit according to the present exemplary embodiment, asdescribed above, nickel has a 1/15 times lower permeability thanmanganese, and thus the number of turns of nickel must be increased toapproximately four times that of manganese to achieve the sameinductance. Accordingly, the nickel must be larger in diameter thanmanganese to achieve the same inductance as manganese.

In the present exemplary embodiment, a method of using a plurality ofinductors is proposed to achieve a high output signal while reducing adiameter of the stylus pen.

FIG. 14 illustrates an equivalent circuit in which two inductors of thindiameter are connected in series and a capacitor is connected inparallel between opposite ends of the two inductors. Hereinafter, thistype of resonance circuit is referred to as an ‘LLC resonance circuit’.In FIG. 14, it is illustrated that two inductors are connected inseries, but the exemplary embodiment is not limited thereto, and threeor more inductors may be connected in series. According to the LLCresonance circuit, since the inductance L is twice as large as that ofthe resonance circuit having one inductor and capacitor (hereinafterreferred to as an ‘LC resonance circuit’), the capacitance may bereduced to half. That is, the LLC resonance may be made to be thinnerthan the LC resonance circuit, but is more sensitive to an influence onthe capacitance.

Meanwhile, FIG. 15 illustrates an equivalent circuit in which two LCresonance circuits are connected in series (hereinafter referred to asan “LCLC resonance circuit”), where two resonance signals are combinedand outputted. In FIG. 15, it is illustrated that two LC resonancecircuits are connected in series, but the exemplary embodiment is notlimited thereto, and three or more LC resonance circuits may beconnected in series.

According to the LCLC resonance circuit, since resonance frequencies ofthe two resonance circuits must be the same, the resonance frequency ofeach resonance circuit must be tuned to be the same in a manufacturingprocess.

As described above, in spite of an increase in the number of windingsgenerated by using nickel as a ferrite core, when two or more inductorsare used as illustrated in FIG. 14 and FIG. 15, a stylus pen having athin diameter may be manufactured by suppressing an increase in thediameter of the inductor unit.

Meanwhile, as illustrated in FIG. 14, when the LLC resonance circuit isused, a stylus pen having a structure described in the following may beadopted to minimize an effect on the capacitance reduced by half.

In FIG. 2, the stylus pen 10 is held by a user's finger or the like, andin this case, parasitic capacitance Cf may be formed by a finger and aninternal conductor (coil or capacitor) of the stylus pen 1.

FIG. 16 illustrates an equivalent circuit showing an effect of theparasitic capacitance Cf by a user's hand. Referring to FIG. 16, aresonance frequency of the stylus pen 10 is changed by the parasiticcapacitance Cf (40). Then, a frequency of the driving signal 30 and aresonance frequency of the stylus pen 10 do not coincide, and thus amagnitude of the signal that is outputted from the stylus pen 10decreases. In this case, an influence of the parasitic capacitance Cf(40) is greater in the LLC circuit illustrated in FIG. 14 than in the LCresonance circuit or the LCLC resonance circuit. This is because, whendesigned with the same resonance frequency, capacitance of the LLCresonance circuit is ½ smaller than that of the LC resonance circuit orthe LCLC resonance circuit.

Hereinafter, a stylus pen for preventing a change in resonance frequencydue to a user's grip will be described with reference to FIG. 17.

FIG. 17 illustrates a schematic view showing a stylus pen of an LLCstructure.

As illustrated in FIG. 17, the stylus pen 10 includes a conductive tip11, a capacitor unit 13, two inductor units 14 and 14′, a blockingmember 17, a ground portion 18, and a body 19.

The inductor units 14 and 14′ include ferrite cores 15 and 15′ and coils16 and 16′ wound around the ferrite cores 15 and 15′, respectively. Inthis case, the two inductor units 14 and 14′ are connected in series.

The blocking member 17, which is a conductive member surrounding thecapacitor unit 13 and the inductor units 14 and 14′, may preventparasitic capacitance from being generated by a user's hand.

In this case, the blocking member 17 may be designed such that oppositeends of the blocking member 17 may be spaced apart along a direction EDof an eddy current in order to minimize an influence of the eddy currentgenerated in the stylus pen.

In this regard, the blocking member 17 will be described in detail withreference to FIG. 18A to FIG. 18D.

As illustrated in FIG. 17, a clockwise current flows through the coils16 and 16′ by a driving signal transferred from the conductive tip 11,and a magnetic field is generated by the currents flowing through thecoils 16 and 16′. In this case, an eddy current is generated in acounterclockwise direction that is opposite to the current direction ofthe coils by a change in the magnetic field generated by the currents ofthe coils, and thus the eddy current in the counterclockwise directionflows in the blocking member 17.

Referring to FIG. 18A, the blocking member 17 includes one slit GP forblocking generation of eddy currents. The slit GP extends along adirection PD that is perpendicular to the eddy current (counterclockwisein FIG. 18). Opposite ends 17 a and 17 b of the blocking member 17 arespaced apart by the slit GP. In exemplary embodiments, the slit GP mayhave a width of 0.03 mm or more along the direction ED of the eddycurrent.

Although the slit GP has been described as extending along the directionPD that is perpendicular to the eddy current, the slit GP may extendalong the direction inclined at a predetermined angle (more than 0degrees and less than 90 degrees) to the direction PD. The opposite ends17 a and 17 b of the blocking member 17 are spaced apart along thedirection ED of the eddy current. Accordingly, since the eddy currentcannot flow along the blocking member 17, generation of the eddy currentis interrupted.

Referring to FIG. 18B, the blocking member 17 includes a plurality offirst blocking units 171. The first blocking units 171 extend along thedirection PD that is perpendicular to the eddy current, and are spacedapart from each other along the direction ED of the eddy current.Similarly, since the blocking member 17 includes the plurality of firstblocking units 171 spaced apart from each other along the direction EDof the eddy current, no eddy current can flow along the blocking member17, thereby blocking the generation of the eddy current. Although thefirst blocking units 171 have been described as extending along thedirection PD that is perpendicular to the eddy current, the firstblocking units 171 may extend along the direction inclined at apredetermined angle (more than 0 degrees and less than 90 degrees) tothe direction PD.

Referring to FIG. 18C, the blocking member 17 includes a plurality ofsecond blocking units 172. The second blocking units 172 are spacedapart along the direction PD that is perpendicular to the eddy current,and opposite ends of each of the second blocking units 172 are spacedapart from each other along the direction ED of the eddy current.Similarly, since the opposite ends of each of the second blocking units172 included in the blocking member 17 are spaced along the direction EDof the eddy current, no eddy current can flow along the blocking member17, thereby blocking the generation of the eddy current.

Referring to FIG. 18D, the blocking member 17 includes a plurality ofthird blocking units 173. The third blocking units 173 are spaced apartfrom each other along the direction PD that is perpendicular to the eddycurrent and the direction ED of the eddy current. Similarly, since thethird blocking units 173 included in the blocking member 17 are spacedalong the direction ED of the eddy current, no eddy current can flowalong the blocking member 17, thereby blocking the generation of theeddy current.

Although the present exemplary embodiment has been described above, theabove detailed description should not be construed as limiting in allaspects and should be considered as illustrative. The scope of thepresent invention should be determined by reasonable interpretation ofthe appended claims, and all changes within the equivalent range of thepresent invention are included in the scope of the present invention.

DESCRIPTION OF SYMBOLS

-   -   10 stylus pens, 11 conductive tip, 12 resonance circuit, 13        capacitor unit    -   14 inductor unit, 15 ferrite core, 16 coil, 17 blocking element,        18 ground portion    -   19 body, 20 touch sensor, 30 driving signal, 40 parasitic        capacitance, 100 enameled wire    -   101 copper wire, 102 enamel, 141 bobbin, 200 litz wire, 201        insulating coating

What is claimed is:
 1. A stylus pen comprising: a body; a tip configuredto be exposed from an inside of the body to an outside thereof; aninductor unit including a ferrite core disposed in the body and a coilwound in multiple layers over at least a portion of the ferrite core;and a capacitor unit disposed in the body to be electrically connectedto the inductor unit to form a resonance circuit, wherein a permittivityof the ferrite core is greater than 0 F/m and less than 1000 F/m, andwherein the coil has a form where adjacent winding layers arealternately wound, and the coil is a wire covering two or more insulatedwires.
 2. The stylus pen of claim 1, wherein the coil is zigzag wound sothat adjacent winding layers are inclined.
 3. The stylus pen of claim 1,wherein the ferrite core includes nickel.
 4. The stylus pen of claim 1,wherein the coil is formed as a litz wire.
 5. The stylus pen of claim 1,further comprising a bobbin configured to surround at least a portion ofthe ferrite core, and the coil is wound on at least a portion of thebobbin.
 6. The stylus pen of claim 1, wherein the inductor unit includestwo or more inductors that are connected in series.
 7. The stylus pen ofclaim 1, further comprising a conductive blocking member disposed on atleast a portion of the inductor unit.
 8. The stylus pen of claim 7,wherein the blocking member includes one slit for blocking thegeneration of eddy currents, opposite ends of the blocking member arespaced apart in a first direction by the slit, and the first directionis a direction in which an eddy current is generated.
 9. The stylus penof claim 1, wherein the inductor unit includes a plurality of inductorsand the capacitor unit includes a plurality of capacitors, a firstresonance circuit includes a first inductor of the plurality ofinductors and a first capacitor of the plurality of capacitors, a secondresonance circuit includes a second inductor of the plurality ofinductors and a second capacitor of the plurality of capacitors, and thefirst resonance circuit and the second resonance circuit are connectedin series.
 10. The stylus pen of claim 1, further comprising a groundportion configured to be capable of being electrically connected to auser.
 11. A stylus pen comprising: a body; a tip configured to beexposed from an inside of the body to an outside of the body; and aresonance circuit disposed in the body, wherein the resonance circuitincludes: a ferrite core disposed in the body; an inductor unitconfigured to include a coil wound in multiple layers over at least aportion of the ferrite core; and a capacitor unit disposed within thebody, wherein a permittivity of the ferrite core is greater than 0 F/mand less than 1000 F/m, the coil is zigzag wound so that adjacentwinding layers are inclined, and the coil is a wire covering two or moreinsulated wires.
 12. The stylus pen of claim 11, wherein the ferritecore includes nickel.
 13. The stylus pen of claim 11, wherein the coilis formed as a litz wire.
 14. The stylus pen of claim 11, furthercomprising a bobbin configured to surround at least a portion of theferrite core, and the coil is wound on at least a portion of the bobbin.15. The stylus pen of claim 11, wherein the resonance circuit is formedto include two or more inductors and one capacitor unit connected inseries.
 16. The stylus pen of claim 15, further comprising a conductiveblocking member configured to surround at least a portion of theresonance circuit.
 17. The stylus pen of claim 16, wherein the blockingmember includes one slit for blocking the generation of eddy currents,opposite ends of the blocking member are spaced apart in a firstdirection by the slit, and the first direction is a direction in whichan eddy current is generated.
 18. The stylus pen of claim 11, whereinthe resonance circuit includes two or more LC resonance circuits thatare connected in series.
 19. The stylus pen of claim 11, wherein theresonance circuit is connected to the tip and to resonate an electricalsignal transferred from the tip, and the coil electrically connected tothe tip.
 20. The stylus pen of claim 11, further comprising a groundportion configured to be capable of being electrically connected to auser, and wherein the capacitor unit is electrically connected to theground portion and the tip.